1. Field of the Invention
The present invention relates to apparatuses and methods in which audio signals are played back and in which audio signals and video signals are played back synchronized with each other, and, in particular, to an apparatus and method that plays back a so-called “AV (audio/visual) signal”.
2. Description of the Related Art
An intensity stereo system having two channels on left and right sides has been used as a system for playing back audio signals. For example, the intensity stereo system, having two audio channels on left and right sides, shown in FIG. 15, is discussed. Of the two audio channels, that is, left and right audio channels, the left channel is hereinafter abbreviated as the “L-ch”, and the right channel is hereinafter abbreviated as the “R-ch”. A speaker for the L-ch is hereinafter abbreviated as an “L-ch speaker”, and a speaker for the R-ch is hereinafter abbreviated as an “R-ch speaker”.
Normally, in intensity stereo recording, sound source signals based on a sound source such as a voice of a singer or movie sound are recorded as audio signals on the L-ch and the R-ch at equal levels and with the same timing so that reproduced sound can be heard from a central position. When reproduced sound is listened to by playing back the audio signals (sound source signals) in a normal manner by using the stereo reproduction system, shown in FIG. 15, having an L-ch and an R-ch, by listening to sounds emitted from the L-ch and R-ch speakers at user positions (listening positions) A and B in front of a central position SPC between the L-ch speaker and the R-ch speaker, the sounds can be heard as if they were being emitted from the central position SPC.
However, when, in FIG. 15, the emitted sounds are listened to at listening positions B and E which are close to the L-ch speaker, the emitted sounds can be heard as if they were being emitted from the L-ch speaker which is close to the user positions B and E. At listening positions C and F which are the listening positions disposed furthest away from the listening positions A and D, the sound emitted from the L-ch speaker can only be heard, the L-ch speaker being closer to the listening positions C and F. Accordingly, despite the fact that sound is being emitted from the R-ch speaker, it is difficult to hear the sound from the R-ch speaker.
This is because of the precedence effect in which, when sound sources emit identical or nearly identical complex signals, a listener perceives a sound image in the direction of a sound that first reaches the listener. Therefore, when a plurality of persons, for example, three persons view a music program or movie, a person in the middle can enjoy sound that is designed to be heard from the central position SPC, which is a localized position of the original sound image. However, each of the two persons on either side of the person in the middle hears sound that is closer to the nearer speaker, so that the sounds emitted from the L-ch and R-ch speakers are heard in an unnatural manner. In particular, when L-ch and R-ch speakers are installed a distance apart in a large room, and when a large screen television set having speakers on two sides of the screen is utilized, such unnaturalness is a problem.
To solve this problem, Japanese Unexamined Patent Application Publication No. 63-26198 discloses a technology which uses the precedence effect and the backward masking method (in which a first-arriving low-loudness sound is masked by a later-arriving high-loudness sound), and in which, as shown in, for example, FIG. 16, by dividing a listening area into three areas, a central area AC, a left area AL, and a right area AR, and using a plurality of directional speakers, a phase inversion circuit, and a delay circuit, a signal arrival time in each listening area and the level of the arriving signal are controlled so that good sound image localization can be obtained in any of the three listening areas.
FIG. 16 shows a case in which each of the L-ch and the R-ch has three speakers having different directionalities, that is, a front direction, a direction inward to the listening area, and a direction outward from the listening area.